1. Field of the Invention
This invention relates to liquid spray nozzles. Although this invention can be used in many different types of spraying systems, it has special application in systems utilizing ceramic nozzle tips.
2. Description of the Prior Art
Spraying nozzles are generally used to atomize liquids. Various kinds of spray nozzles have been known for a considerable time. For example, an airless type spray nozzle can be formed from a nozzle tip hydraulically connected to a source of pressurized liquid. The nozzle tip has a passage through it. An inlet end of the passage is supplied with liquid under pressure. The shape of the passage gives rise to forces and flow within the liquid stream causing turbulence and high velocity. This causes the liquid stream to be broken up into a multitude of small droplets in a special pattern upon discharge from the tip. The high velocity is caused by a restricted orifice in the nozzle tip passage at the discharge or outlet end of the nozzle tip. It should be noted here that the functional mechanics of the nozzle tip are generally described here only as a matter of background, and form no part of the invention. Reference can be made to U.S. Pat. No. 3,556,411 for a more detailed description.
Because of the high velocity caused by the restricted orifice, a nozzle tip is subject to abrasive wear at this point. Therefore it is desirable to form the nozzle tip from an abrasion resistant material. However, because many abrasion resistant materials such as ceramic are brittle, it is desirable to connect the nozzle tip to the supply of pressurized liquid by means of a nozzle tip holder which can be made of less brittle material and which provides protection and support for the nozzle tip.
The nozzle tip holder in the past has taken various forms, and was, in a simple form, in the shape of a ring, or a disc with a hole or passage in the middle. The nozzle tip was either glued or brazed into this hole in the tip holder.
Brazing or gluing of the nozzle tip in the holder performs satisfactorily for a large number of applications. However, recently there have been applications in which brazing or gluing was not acceptable. For example, there are processes which require the nozzle tip to be in an environment of very high temperature. In such applications the glue or brazing would melt. However, in these applications it is still sometimes desirable to use a small ceramic nozzle tip supported by a holder which would give strength and protection to the tip without making the whole assembly brittle. In such a situation a completely mechanical joint between the tip and the holder would be desirable. However any such mechanical joint must not exert undue stresses on the brittle ceramic tip lest it would fracture.
Further, even in situations where high temperature is not a problem, a completely mechanical joint between the nozzle tip and the tip holder is desirable. One example would be in the can industry. Recently there have been numerous regulations governing contamination of the interior of cans which will be used for food. The completely mechanical joint for the nozzle tip in a system used to coat the inside surfaces of cans reduces the number of possible contaminants, specifically the glue or the brazing material.